A variety of mobile radio communication systems is conventionally known. Such systems include WCDMA (Wideband Code Division Multiple Access), LTE (Long Term Evolution), and LTE-A (LTE Advanced), standardized by 3GPP (Third Generation Partnership Project), and WiMAX (Worldwide Interoperability for Microwave Access) standardized by IEEE 802.16 committees. In these mobile radio communication systems, a coverage area of base-station apparatuses (a base station, a transmission station, a downlink transmitter apparatus, an uplink transmitter apparatus, eNodeB) or a transmission station functioning in practice as a base-station is cellular-structured into a plurality of cells to expand a communication area.
With frequencies different between adjacent cells or between adjacent sectors used, terminal apparatuses (a mobile station, a receiver station, an uplink transmitter apparatus, a downlink receiver apparatus, a mobile terminal, and UE: User Equipment) in a cell edge area or a sector edge area may perform communications in a manner free from interference from signals transmitted from a plurality of base stations. However, in such an arrangement, a frequency usage rate is low. On the other hand, the use of the same frequency on adjacent cells or on adjacent sectors may increase the frequency usage rate. In such a case, however, a remedial step becomes necessary for a terminal apparatus in the cell edge area against interferences.
More efficient data transmission may be achieved by adaptively controlling a modulation method and an encoding ratio (MCS: Modulation and Coding Scheme), spatial multiplexing count (the number of layers, and ranks), and precoders in response to a transmission status between a base station and a terminal apparatus. Non Patent Literature 1 below describes the method of controlling the modulation method and the encoding ratio.
FIG. 13 illustrates a base station 1301 and a terminal apparatus 1302 in the LTE. When MCS, the spatial multiplexing count and the precoder are adaptively controlled on a transmitted downlink transmission signal 1303 in the LTE of FIG. 13, the terminal apparatus 1302 performs the following process. Specifically, the terminal apparatus 1302 calculates reception quality information by referencing a downlink reference signal (RS: Reference Signal) included in a downlink transmission signal 1303 transmitted from the base station 1301. The reception quality information typically includes a rank indicator RI (Rank Indicator) specifying an appropriate spatial multiplexing count, a precoding matrix indicator PMI (Precoding Matrix Indicator) specifying a preferred precoder, and a channel quality indicator CQI (Channel Quality Indicator) specifying an appropriate transmission rate. The terminal apparatus 1302 reports the calculated reception quality information to the base station 1301 via an uplink channel 1304.